Allison 3000 Transmission Running Hotter than Normal in 2005 Beaver Monterey

[Bryan Schmidt]

Looking for suggestions as what else to check to see why our MH3000 Allison transmission is running hotter than it’s past 10 yr history?

Short past coach history: 2005 36’ Beaver Monterey Ventura IV with a Cat C9, with 27K miles on it.   Nominal running temps over the past years: engine 186 deg & TX 166 deg.  Hottest ever recorded: Engine 203, TX 201 years ago.    On our last major return trip home in Oct2015 down I-5, I noticed the Allison 3000 TX was running noticeably hotter than for the last 10 years, consistently up in the 188+ range.  Once home, I discovered that the Sauer-Danfoss hydraulic fan pump/motor bolted to the curbside of the Allison was leaking at the bolted joint between the 2 major subassemblies of the pump/motor.  That pump leak was ultimately fixed, due to recommendations for locating a replacement gasket solely from folks on this forum.   I thought the problem was fixed.

Yesterday, I took the coach out for a test run since we had not had it out for last 4 months due holidays and a major renovation job in the house.  As noticed before the pump leak repair, the Allison ran almost the same temp as the engine, up in the upper 178-182 (still not the same as it’s past history), this being on flat sections as well as multiple climbs, (one up to 1.75+ mile long), while still going at 50+ MPH along the coast.  Ambient air temp was 55 degs.  I stopped several times during the drive, checking for leaks and trying to hear if the hydraulic fan was running.    Peering inside of the engine compartment, I couldn’t directly see the fan actually ever running since its shrouded, nor did I seem to hear it running, but maybe I just checked it at inopportune moments.  (Note: I don’t know what temp the hyd radiator fan is supposed to kick in and be running.)    Also while stopping, I noticed the TX temp bump up a few degrees at each stop, and then it would drop back down once moving again.

The last  mile to our house is a twisty, skinny 2 lane asphalt road, consistent up hill 4%+ grade and I can only go about 15MPH up to due to limited visibility around several blind curves.  At the bottom on the hill, the engine temp was 171 & the TX temp was 180.  After the slow slog last mile, up hill w/ engine running at 95%+, engine temp was 176 and TX temp was 195: a 15 deg spike!

Does this consistent running hotter while moving and then excessive jump in TX fluid temp over a slow, 1-mile climb, w/ engine lugging, seem indicative of a hydraulic fan system failure?   I guess it could be the pump/motor itself , the fan assembly, a plugged filter, etc.    Or something else?

Things I’ve checked so far:
- Repaired external Sauer-Danfoss hyd pump shows no signs of new leakage, but that doesn’t mean that its actually working/pumping correctly either.  I also do not see any new oil/fluid dripping or wet spots indicating a possible leaking/busted hose, fitting, etc under/around the engine, TX or radiator areas.

- TX fluid level, from the key pad:  good.  Level sensor seems to be working correctly, initially giving a “o L – 0 7” for fluid temp too low, and once fluid was above approx 140 deg, key pad went through its normal (7) 15 sec interval countdown and received the “o L - O K”.  Note: After the above hyd pump was repaired in late2015, I did manually topped off and checked the TX fluid level via the dipstick, and also compared it at that time with the TX fluid keypad readout of “o L - O K”

- Hydraulic fluid level: good.   Fluid still seems to be clear red.  Hyd fluid filter last changed 3k miles & 18 months ago. 

- Engine coolant (ELC changed 4 yrs ago) seems to still be good color, level is good, & I can look into the coolant overflow tank and see coolant circulating back into the tank via the overflow tube

- Is there an ease way to actually see if the radiator fan turning, or, at what temp/sensor event triggers the fan to turn on?  I was assuming the engine coolant temp above some set level (e.g.: 180 deg?) was the trigger event.

Any suggestions as to what else to look at before trying to locate a qualified repair shop on the Oregon coast / Southern Oregon area would be greatly appreciated.

Thanks..

Bryan

[Gerald Farris]

Bryan,
It does not sound like you have a problem since none of the temperatures that you listed are excessive. Some of the conditions that you listed are normal like the transmission temperature rising at a stop when idling in gear but decreasing when moving again. What type of transmission cooler is your coach equipped with?

The only thing that I would suggest that you do is to have a fluid analysis ran on your transmission fluid to determine it's condition and check for contaminates. If it checks OK, you have nothing to worry about.

Gerald

[Steve Huber Co-Admin]

Bryan,
I've got an 07 43' Contessa with the 400 HP C9 mfg in 06 and 3000 tranny. The C9 consistently  runs at 204-206 with tranny in same range when on the open road. CAT specs engine thermostat to start opening at 188 and be fully open at 206, (Thx to D. Atherton for checking w/Cat). The Check Engine sensor for engine temp is set somewhere north of 225.  With our coach being heavier than yours. the increased temps are probably understandable plus CAT may have increased op temps to meet emission stds between mfg of your engine and mine. I previously had an 01 Contessa with a 3126B. After flushing the cooling system and new coolant, it constantly ran 3 degrees hotter. Never could figure out why.  In any case, I agree with Gerald. Don't think there is anything to worry about.
Steve

[Joel Ashley]

I am no expert here, and was kinda waiting for others to comment.  Sounds like they pretty much support what I've read on the Forum in previous threads, and I can proffer my experience with our own coach that's similar to yours, Bryan.  The numbers you report are almost identical to what I've seen on ours, which has averaged close to 200 degrees for both engine and tranny since new, so I wouldn't fret it too much.  Things seemed to run a smidge cooler after upgrading to Transynd and ELC.

I really liked our experience with Henderson's in Grant's Pass, but I don't know how much they're into transmissions.  If still concerned, you could call and run it by them.  Robert Henderson is quite chassis knowledgeable and is good about discussing such over the phone. 

Pacific Truck Center in Medford is an Allison service facility also.

Joel

[Bryan Schmidt]

Gerald, Steve & Joel..

Thanks for the feedback on "normal" running temps and suggestions. 

I'll be getting both the Transyn fluid & ELC coolant analyzed (CAT SOS test kit) just because they both "look" right does not mean they still are right after 4 yrs since being last serviced and changed out...  Spot on suggestion..

Guess I just was spoiled for all the past years running full loaded and towing with the TX rarely braking 180s in mid summer, be it climbing I-70 Eisenhouser Pass or the back road Rocky Mt passes to the ski areas, or whatever. 

At what engine and TX temps do you guys start getting concerned when driving, especially running in the summer months with air temps at 90+ And longer hill climbs?

Gerald: I could not find the vendor/model number on the TX cooler, but it is the original Breaver install.   You asking about it caused me to think when was the last time I cleaned/flushed externally the CAC and TX radiator fins.  Something else to get after.  We'll see what the TX fluid analysis comes back with.

Joel: Since moving to OR, I've used Hendersons for all of the coach heavy maintenance & lube.  Last year, we had Henderson's upgrade the chassis front end and all around suspension, and that alone made a huge positive driving enhancement.   First time my wife rode in the coach after the upgrade, she thought something was wrong since she thought I was going far below the speed limit - all the body roll, swaying, front end diving, and overall coach ride was so smooth and quiet.    I did talk to Hendersons and they sent me also to Pacific Truck Center or Petersons Cat, both in Medford for any engine or TX work..

Wife says not to worry, it's just arthritis setting into Allison since she's getting "old" like us...

Thanks again...

[Jerry Emert]

Bryan, I attended the Monacoers Rally in Tampa a month or so ago.  There was a session on Allison Transmissions.  I've had a lot of questions about my trans. temps so I asked basically the same question.  What temp should make me worry.  The Allison Rep. said that spome of the OEMs set different temps for an alarm point.  The most often seems to be 250.  He said that some of the heavy trucks with basically the same transmissions that we use have run over 300 for extensive periods with no damage.  He said not to worry about it until at least 250.  Still worries me some.  Mine normally gets up to 215 or so after radiator and CAC cleaning and change to ELC.  It was a little higher before.  Good luck.
Jerry

[Steve Huber Co-Admin]

Bryan,
With temps that run in the 180-190 range on the flat and level, when climbing steep or long grades in summer heat, be sure you downshift and keep the RPMs up (I normally like to keep them at >1800) as that keeps the water pump and fan running fast. Temps may rise to 205-210 on very severe hills but I suspect your Check Engine is set for about 215. Again, key is to keep RPMs up and not worry about speed. On some climbs going north out of Phoenix, I'm in 3rd a lot of the time of the grades. As long as Check Engine doesn't come on, you're OK. If it does and then goes out shortly after when the engine drops a degree or 2, don't worry either.
Steve

[David T. Richelderfer]

Our coach came to us with an auxiliary transmission cooler.  We do not know which prior owner had it installed, nor where, nor when, nor which manufacturer made it.  Anyways, the highest transmission temperature we have seen is about 138F to 140F.  The transmission temperature runs from 35 to 50 degrees over the outside ambient air temperature.  On cool days the transmission temperature barely gets over 100F.  The transmission keypad will not report the oil level status until the oil temperature exceeds 140F.  Therefore, we have not been able to easily check the transmission's oil fill status regularly.  We are wondering if a too cool transmission oil temperature may be bad and also wondering if a too cool transmission oil temperature may be contributing to the poor mileage our coach gets - from 4.5 to just over 6 mpg (rarely - twice in 3 1/2 years), usually it's 4.8 to 5 mpg.

Anyways, if the hot temperatures are a problem, then get an auxiliary cooler.

[Harold and Gloria Skipworth]

I noted that you had the Sauer Danfloss pump repaired and since I suspect than my pump has a seal leak which allows transnyd to enter the hydraulic fluid tank and overfill the tank.  I wondered where you got the pump repaired.

[Bryan Schmidt]

Skip:

I'm hoping that you have found the following past post on the Sauer-Danfoss hyd pump leak...

http://beaveramb.org/forum/index.php/topic,4424.0.html

Once I was pointed in the right direction by 2 of the guys on the forum here, to the correct pump gasket, via the correct p/n, which cost a whole $5, I thought about doing it myself, but we were getting close to leaving for our next trip.   So the DW "helped" to change my mind since I had too many other "got to get done so we can leave in 3 days" items on the departure checklist.

I was able to get Beaver into my small local car/rv repair place.  Once I called them, they knew right way what the leak was and they said they had repaired several Monaco coaches with the same leaky pump over the last 3 years.  Luckily the replacement gasket had just arrived.   I dropped the coach off the next morning at the garage and they had the pump pulled, gasket repaired and pump reinstalled in 90 mins.  The pump hasn't leaked since. 

Lee Welbanks, the initial author of the above post, did the gasket repair himself.    The correct gasket number is also listed in the original above post...

Bryan

[Adam Hicklin]

A small aside for clarification, and not to take this on a tangent but... I've heard a few times on this forum about keeping the engine rpm up to facilitate cooling of both engine coolant and transmission.  With an engine driven fan this makes sense, but this fan is hydraulic, independent of engine rpm, isn't it? Seems like I've also heard that the hydraulic fan has two speeds determined by temp. sensors of engine coolant. As Steve said, I can understand rpm affecting water pump speed, hence moving more coolant, but not cooling fan speed.  What am I missing?

[Edward Buker]

Adam,

There is a boost in hydraulic pressure given the pump is driven off of the engine and the output/flow is therefor engine RPM related. The water pump on the engine is also direct driven and the flow rate is also RPM related. The more passes/heat exchanges the antifreeze makes through the radiator in a given time the more the heat can be exchanged with the air.

If you are climbing a hill at low RPM vs High RPM in a lower gear the energy required to move the coach up the hill for the most part is the same but with the high RPM climb the hydraulic driven fan speed and antifreeze flow is increased while the heat byproduct of the energy consumed to climb is more a constant.....So better cooling at higher RPM. Hope this helps.

Later Ed

[Harold and Gloria Skipworth]

I was hoping you had actually had the pump repaired as my pump and pto have no visible leak. My Allison suspects transyd passes through the pump shaft seals ultimately overflowing the hydraulic tank and starving the trans converter which causes lousy acceleration till I get to 2L gear.  All of which I experienced.

[Jim Edwards]

HI Brian, this should probably be in a different thread but can you tell me what Henderson did to your front end? We are on the east coast and I have been thinking on having them work n it but I question if it is worth a trip? Thanks

[Joel Ashley]

Bryan may have had work done similar to ours, Jim;  it certainly improved our handling, and side-to-side torsion and bump response. 

Henderson's switched us to Koni shocks, added a Safe-T-Plus for my peace of mind, put their little SuperSteer motion control valves in place to augment the air bag response, and tweaked the steering gear.  Our coaches don't benefit from their aftermarket bellcrank, and the steering is adjustable, so no need to buy that - they just road test and adjust as necessary. 

That said, they do offer a unit for trimming the Safe-T-Plus, but we used to have a STPlus on our old Pace Arrow sans any trim unit, so I didn't go in for it this time either;  the coach is so improved, any road crown or wind trimming just wasn't necessary for me given the additional cost.  Maybe sometime in the future if I get aggravated at truckpass or other wind influence or something, I'll add the trim unit, but wind response improved with just what they already did.

Their Road Performance Accessment was well done, a learning experience, and much appreciated.  But if you aren't up for the trip to benefit from their work, you might call them and ask if they know of a vendor on the east coast they'd recommend.  Parts: (541) 955-0769       Service: (541) 326-4033

Joel